(a) Technical Field of the Invention
The present invention generally relates to a spoke with enhanced fatigue resistance, and more particularly to a spoke that allows for, in a process of assembling a spoke body to a wheel hub and a wheel rim, the use of a combination of a first flattened section and a second flattened section to set the spoke body at a correct position and direction for assembly and force taking, whereby the first flattened section absorbs torsion and the second flattened section helps transfer tension and allows for change of the angle of bending so that the spoke body, when put into use, effectively absorbs or transfers shock waves transmitted thereto and thus significantly enhancing the capability of the spoke body for fatigue resistance and greatly reducing the chance of the spoke body getting broken
(b) Description of the Prior Art
A traditional spoke 6 (as shown in FIG. 7) used in a bicycle or a motorcycle comprises a bend section 61 and a threaded section 62 and the bend section 61 has a fixed angle a. Such an arrangement has been widely used in the industry. However, it is not popularly used in wheel sets that have less numbers of spokes 6. This is because it is found by manufacturers and assemblers that the bend section 61 often gets broken easily and abnormally. A guess has been made, according to experiences, that the bend section 61 having insufficient resistance against fatigue is the major cause of the occurrence of the abnormal breaking. However, although there are a huge number of abnormal breaking events, there is still no way that a correct explanation can be obtained empirically and repeated tests have been adopted to identify that instantaneous torsion and tensions of abnormal angles at the portion below the bend section 61 are primary factor for the easy and abnormal breaking. Thus, improvements have to be made in respect of the torsion and the angle in which forces are applied thereto.
Further, the angle a of the spoke 6 is normally specified in the industry. For a spoke having a diameter of 2.0 mm, the angle a of the bend section 61 must be set 95 degrees. This makes the angles of the bend sections 61 consistent, simplifying the process of manufacture of the spokes 6 and also allowing for efficient assembly of the spokes 6 and thus reducing stocks of the workshops.
However, when a spoke 6 is put through a through hole 411 of a hub 4 to be assembled to a threaded section 51 of a wheel rim 5 (as shown in FIG. 8), at least two different angles are needed for the bend sections 61 because in actual assembly operations, different wheel radii require different angles of the bend sections 61 and incorrect angle of the bend section 61 will affect the strength of the spoke 6, leading to an obvious reduction of the fatigue resistance of the spoke 6 and eventually causing easy happening of breaking of the bend section 61.
Further, there are other known spokes, which are respectively designated by reference characters A and B in FIGS. 9 and 10, in which a flattened bend section A3, B3 is formed between a middle section A1, B1 and a terminal section A2, B2 for the purposes of improving the above-discussed drawbacks. In actual tests, the traditional spoke 6, the known spoke A, and the known spoke B are subjected to fatigue tests under the condition of 180 kgf/10 Hz for cyclically repeated stretching and releasing. The result of the tests indicates the average performances of these known spokes are respectively 11,632 cycles, 21,133 cycles, and 6,472 cycles. The traditional spoke 6 is easily broken at the bend section 61. The known spoke A has a flattened bend section A3 that possesses better fatigue resistance, but is hard to be assembled to a wheel hub and may causes an abnormal angle with respect to the wheel rim, leading to easy breaking of the threaded section. Further, the known spoke B has a flattened bend section B3 that is extremely easily broken and shows a capability of fatigue resistance that is worse than the traditional spoke.
The above-described tests reveal that the traditional spoke 6, the known spoke A, and the known spoke B all possess shortcomings in assembling and use.